Clutches of the above type are described, in particular, in the specifications of U.S. Pat. Nos. 3,907,085 and 4,102,446, and in that of United Kingdom published patent application No. GB 2 147 668A. In these arrangements, during disengagement of the clutch the reaction force which is exerted by the said other element of the hydraulic control means is transmitted to the cover plate.
In other clutches, for example that described in particular in the specification of U.S. Pat. No. 3,540,557, this reaction force is transmitted to the casing of the gearbox.